This invention relates to a security viewing device for installation in a door, of the type used by the resident of a dwelling to establish the identity of a caller before opening the door.
Securing viewing devices to enable the resident of a dwelling to survey the identity of a caller before opening the door trace their origin back to the peephole. Although such devices have been refined, for example, by the inclusion of wide angle vision lenses to increase the field of view and by one way glass to conceal from the caller the fact that he is being observed, such devices still generally provide a restricted field of view. This restricted field of view can, on occasion, be exploited by unwelcome callers. For example, it is not unknown for criminals to work in pairs so that a resident summoned to his door may see through his viewing device only an apparently harmless caller, such as a child, whereas a criminal accomplice may be standing to the side of the door out of the field of vision waiting to gain entrance.
To avoid such disadvantages arising from the ability of a caller to position himself outside of the field of view of most existing viewing devices, it would be desirable to expand the resident's field of view so that it extended not just outwardly of the door but also sidewardly across its surfaces. Other qualities that should be sought for in a security viewing device are silence of operation and simple construction.